The first big Dutch project to store excess CO2 under the North Sea is now set to cost at least €1.3 billion, almost triple the first estimate of €500 million when the project was launched five years ago, the NRC reported on Friday.

The rise is due to inflation which has pushed up costs of preparing the location for storage, the three state-owned companies behind the Porthos project – Gasunie, Rotterdam’s port authority, and EBN, said.

Delays have also been caused to the project by a court case brought by campaign group Mobilisation for the Environment, which argued too much nitrogen would be released during the construction process. 

Last August, the highest Dutch administrative court gave the green light to the controversial project, saying it would lead to more nitrogen-compound pollution but that it would be temporary and would not have a major impact on the environment. 

The carbon capture project, named Porthos, involves pumping the CO2 via a pipeline from the Rotterdam port area to the empty gas chambers some 25 kilometres offshore. The aim is to store 2.5 megatonnes of CO2 a year – or 1.5% of total emissions.

Construction is due to start this year and storage to begin in 2026.

The CCS project will be a first for the Netherlands. Earlier plans by Shell to use empty gas reservoirs under Barendrecht were shelved because of local residents’ concerns. 

Shell and Total are working on an even bigger project together with Gasunie and EBN given the code name Aramis, the NRC said.